Return values:

withAppId(appId)

Sets the ID of the mobile application. This field is required. The ID is a string that uniquely
identifies a mobile application to AdWords API. The format of this string is
"{platform}-{platform_native_id}", where platform is "1" for iOS apps and "2" for Android apps,
and where platform_native_id is the mobile application identifier native to the corresponding
platform. For iOS, this native identifier is the 9 digit string that appears at the end of an
App Store URL (e.g., "1091700242" for "Gboard" whose App Store link is
https://itunes.apple.com/us/app/gboard-new-keyboard-from-google/id1091700242). For Android,
this native identifier is the application's package name (e.g., "com.google.android.vr.home"
for "Daydream" from the Google Play link
https://play.google.com/store/apps/details?id=com.google.android.vr.home). A well formed app ID
for AdWords API would thus be "1-1091700242" for iOS and "2-com.google.android.vr.home" for
Android.